a!isUserMemberOfGroup throwing InvalidUserException

Hi All,

I am getting error in below expression 

a!localVariables(
           local!userName: "xyzUser",
           if(
                isusernametaken(local!userName),
                a!isUserMemberOfGroup(local!userName, cons!PP_GROUP_CONSTANT),
                0
              )
)

Error as

Expression evaluation error at function a!isUserMemberOfGroup [line 5]: [InvalidUserException]

I observed this issue with deactivated user in only one environment where in lower environment its working fine with deactivate users as well.

Thanks in Advance!